In the data storage arts, the term “RAID” stands for a “redundant array of inexpensive disks” (or alternatively a “redundant array of independent disks”) and refers to a system that uses multiple hard drives to share or replicate data. In its original implementations, the key advantage to a RAID system was the ability to combine multiple low-cost devices using older technology into a storage disk array that offered greater performance than what was affordably available in a single device using the newest technology. Depending on the RAID version chosen, the benefits of RAID systems include (as compared to single drives) one or more of increased data integrity, fault-tolerance, throughput and capacity.
A RAID system is typically used on server computers, and is usually (but not necessarily) implemented with identically-sized disks. However, with decreases in hard drive prices and wider availability of RAID options built into motherboard chipsets, RAID is also being found and offered as an option in more advanced personal computers. This is especially true in computers dedicated to storage-intensive tasks, such as video and audio editing.
Two particular RAID levels of interest, known as RAID 4 and RAID 5, operate by distributing data over a plurality of disk with redundant parity information assigned to a single disk (RAID 4) or distributed among the various disks (RAID 5). Some of the primary advantages to RAID 4 and RAID 5 systems are that large amounts of data can be quickly offloaded to external devices while the failure of a single disk could be handled albeit with some performance degradation.
Unfortunately, when a disk does fail in a RAID 4 or RAID 5 system, it is necessary to replace the failed disk and reconstruct the lost data using the remaining disks, a task that can be very difficult if the RAID is busy delivering large amounts of data over long periods of time, and very important as the loss of another disk in the interim would mean a loss of all of the data on the RAID system. Further, present RAID 4 and RAID 5 systems are not well suited for high-speed streaming data, especially in the event of a failure. Thus, new technology related to improving RAID performance is desirable.